Method of manufacturing a heat exchanger

ABSTRACT

Method and apparatus for mounting fins unto pipes for a heat exchanger comprising the steps of placing a predetermined number of pipes into the orifices of one or more fins, the outer diameter of the pipes being less than the orifices, sealing liquid in said pipes, and heating said liquid to a superheated vapor to expand said pipes so as to expand the outer diameter of the pipes to tightly fit within the orifices.

United States Patent Kimura [54] METHOD OF MANUFACTURING A HEATEXCHANGER [72] lnventor: Keiichi Kirnura, 2-304, Osakabe, Yao,

{apan [22] Filed: Dec.24,1969

[21] Appl.No.: 887,826

Related US. Application Data [63] Continuation-impart of Ser. No.649,325, June 27,

1967, abandoned.

[52] U.S.Cl ..29/l57.3V, 29/1573 A, 29/421,

[51] Int. Cl ..B2ld 53/02 [58] Field of Search ..29/157.3 A, 157.3 V,421; 113/118 A [56] References Cited UNITED STATES PATENTS 2,119,9606/1938 Price ..l13/118 R Feb. 29, 1972 2,458,189 1/1949 Morgan 29/1573A/H X 3,432,905 3/1969 Monroe. ..29/157.3 A

3,572,073 3/1971 Dean ..29/421 X FOREIGN PATENTS OR APPLICATIONS 10,9867/1916 Great Britain ..29/421 Primary ExaminerJohn F. Campbell AssistantExaminer-Donald C. Reiley, lll AttarneyMoonray Kojima [57] ABSTRACTMethod and apparatus for mounting fins unto pipes for a heat exchangercomprising the steps of placing a predetermined number of pipes into theorifices of one or more fins, the outer diameter of the pipes being lessthan the orifices, sealing liquid in said pipes, and heating said liquidto a superheated vapor to expand said pipes so as to expand the outerdiameter of the pipes to tightly fit within the orifices.

9 Claims, 7 Drawing Figures Patented Feb. 29, 1972 3,644,975

3 Sheets-Sheet 1 INVENTOR KEHCH/ KWURA AT T.

Patented Feb. 29, 1972 3,644,975

5 Sheets-Sheet 2 INVENTOR KEHCHI KHIURA ATT.

Patented Feb. 29, 1972 3,644,975

3 Sheets-Shet 5 INV-ENTOR KEHLH KIMURA g ATT.

METHOD OF MANUFACTURING A HEAT EXCHANGER RELATED APPLICATIONS Thisapplication is a continuation-in-part application to application Ser.No. 649,325, filed June 27, 1967, and to be abandoned shortly.

This invention relates to the method and device for manufacturing a heatexchanger provided with such fins, for example, as thermal radiationplates or endothermic plates substantially usable for the fundamentalelements of a heating and cooling apparatus, an air-conditioningapparatus, a condensing unit or the like.

conventionally speaking, it is a matter of common practice that a heatexchanger is manufactured by thermally sealing these fins toheat-exchanging pipes so as to enhance the thermal conductivity of thewhole system. Accordingly, many attempts and experiments have so farbeen made for the purpose of satisfying the above-mentioned practicalrequirements for manufacturing the heat exchanger; and especially theproposition has been made, for instance, firstly of the method thateither liquidlike oil or air is sealed into a continuity of pipe underhigh pressure so as to cubically expand said pipe and fix the finsthereto; in the second place, the method that liquid sealed in the pipeis condensed until this pipe is cubically expanded and rigidly securedto the fins, as is taught by the US. Pat. No. 2,458,189; and thirdly,the method as is disclosed in the US. Pat. No. 2,119,960 that liquid issealed into a pipe under high pressure and at the same time heated untilthe fins are thennally sealed to the pipe. However, according to theabove-mentioned first method in which either oil pressure or airpressure is used to inflate the pipe, it is necessary to provide a largescale pipe swelling equipment and the technical deficiency is fatallybrought about that accuracy of thermal sealing is not altogethersecurable substantially because of the frequent occurences that theforce to cubically expand the pipe fails in coming up to a satisfactoryextent.

According to the second method in which liquid is congealed until thepipe is cubically expanded, it is impossible to distribute the coolingeffect of a refrigerant over the fixed overall length of the pipe. Thusthis second method fails to secure the uniformity of the cubic expansionof the pipe, giving rise to the deficiency that the fins cannot be fixedin uniformity to the pipe and consequently necessitating a large scalepipe cooling equipment in order to obtain the completely uniform coolingeffect upon the pipe.

The third method may have the advantage over the first method in thatthe liquid sealed under pressure is heated until the pipe is cubicallyexpanded. However, as has been specified in the U8. Pat. No. 2,119,960,the liquid is preferably heated to an extent not exceeding the boilingpoint. Thus this third method is merely employable for the purpose ofheating a liquid feed conduit connected to the pipes which heats theliquid body; this is partly because said method prevents the fins frombeing overheated and partly because it can provide a better conveniencewhere the liquid body is heated to a desirable value, that is, to such atemperature not exceeding the boiling point. Therefore, it is easilyunderstood that said third method intends in essence to inflate the pipemainly by utilizing the high pressure or superhigh pressure under whichthe liquid is forcibly sealed into the pipe; due to this, the heatingoperation is merely an essence auxiliary to this method. This will alsobe easily comprehended from the fact that when this third method isapplied, the cubic expansion of the liquid is very a little expectedsince the temperature of the liquid to be heated is exclusively limitedbelow the boiling point. However, in order to seal the liquid into thepipe under high pressure or superhigh pressure which is the main elementof the third method for inflating the pipe, said method needs installinga large scale pipe swelling equipment just like in case with the firstmethod and what is more such an equipment takes very troublesomeoperations. Thus the defect of said first method cannot still beeliminated by this third method.

The present invention aims at disrooting the deficiencies caused by theabove-mentioned conventional methods for cubically expanding the pipe;and the method of this invention is to produce vapor by effectivelyheating the liquid sealed in the pipe and cubically expand the pipe byusing the endlessly continued cubic expansion of this vapor, withoutemploying the method of swelling the pipe by forcibly sealing the liquidinto the pipe under pressure.

Especially the principal objective of the invention is to provide themethod of effectively and easily manufacturing a heat exchanger by useof either the thermal radiation plates or endothermic plates insertedthrough the heat-exchanging pipes so that the water in the pipe isvaporized with high effect and promptness to cubically expand the pipeby means of said endlessly continued cubic expansion of the vapor.

Another objective of the invention is to provide the method of aneconomical-type heat exchanger in which the thermal radiation plates orendothermic plates to be inserted through the pipes can be heated withmore highly enhanced efficiency than the conventional method thereby toincrease in a heating effect; and the thermal energy produced while saidplates are being heated is utilized in the most effective manner.Further another objective of the invention is to provide such an easilyoperable device of much simplified structure that can continuously carryout the above-mentioned method of manufacturing a heat exchanger withhigh efficiency and promptncss.

As has been referred to above, it is a well known art in general tothermally inflate the heat exchanging pipe by heating the liquid sealedin this pipe. However, this pipe inflating method depends exclusivelyupon the cubic expansion of water and therefore it is impossible toexpect a favorable result of cubically expanding the overall length ofthe pipe in uniformity merely by using this expansive power of theliquid or water. Conversely, according to the method of the presentinvention, it has no need of forcing the liquid into the pipe under sucha high pressure as to give the cubic expansive power to the liquid,since the liquid sealed in the pipe is promptly and effectively changedinto vapor by absorbing the thermal energy from the fins regularlyspaced on the pipe with the result that the pipe is inflated by thecubic expansion of the vapor.

When the method of this invention is carried out, the fins arepreferably heated by blowing a hot blast; but they are not to be heateddirectly by means of a burner or the like. According to this invention,the pipe is inflated equally through its full length thereby making itpossible to manufacture a heat exchanger in such a manner that duringthe inflation of the pipe even a single part of this pipe is nottransformed nor damaged.

The device by which the foregoing and other objectives of the presentinvention are accomplished and the method of their accomplishment willbe readily understood upon reference to the accompanying drawing, andthe novelty and characteristics of the invention are as pointed out inwhat is claimed.

In the accompanying drawing:

FIG. 1 is a diagrammatical illustration of a device to be used forembodying the method of the present invention,

FIG. 2 is a side elevation showing a base pattern of such an unfinishedheat exchanger that has not been conveyed to be thermally sealed, and inthis elevation fins are shown in lines,

FIG. 3 is a side elevation showing another type of the base pattern ofan unfinished heat exchanger as against the base pattern shown in theFIG. 2,

F16. 4 is a plan view of a fin to be used in this invention,

FIG. 5 is a cross-sectional view taken on line V-V thereof,

FIG. 6 is a plan view showing another type of a tin to be used in theinvention and,

H6. 7 is a cross-sectional view taken on line Vll-Vll thereof.

Setting forth one of the methods of the present invention with referenceto the accompanying drawing, a desired number of heat-exchanging pipes 1and l are provided with a plurality of regularly spaced fins (which willbe referred to hereinafter) having holes of a little larger diameterthan the outer diameter of said pipes. With exemption of the two pipeopening ends 1' and 1" which serve for an inlet and an outlet for arefrigerant respectively, all the other pipe opening ends are connectedwith bend pipes 3 by means of welding or the like in such a manner thatsaid pipes form a single passageway for the refrigerant running fromsaid inlet as far as said outlet.

If circumstances require, hairpin pipes 4 may be replaceable with thebend pipes. In this case, frame means 5 and 6 are mounted on both endsof the base pattern of a heat exchanger as shown in FIG. 3, and securedto each other by means of nuts 8 and supporting rods 7 tightened eachother. In the second place, one of said two pipe opening ends 1' and 1"is closed and water or any other suitable kind of liquid is forciblyinjected from the other pipe opening end. After injection, said otherpipe opening end is closed thereby sealing the injected water or liquidin the pipe. This injection is made possible by increasing the pressureof preferably about 25 Kg/cm. for instance by means of a pump P. Thisforcible injection of water or liquid under increased pressure isnecessary, not for cubically expanding the pipes nor for promoting theinflation of the pipes, but for eliminating air bubbles from the waterto be injected, which otherwise will prevent the pipe from beingeffectively swelled. Said pump or other substitute means is notnecessarily required for the above-mentioned purpose. As has beenmentioned above with reference to FIG. 2 and 3, the unfinished fins 2 inwhich water is sealed forms a base pattern A of a heat exchangerunfinished or in the making which has still not been secured to thepipes 1. For conveniences sake of the following explanation, the basepattern of a heat exchanger unfinished or in the making will be calledmerely the base pattern in abbreviation hereinafter. Thus this basepattern that will be worded in the following paragraphs is to be notedall as designating the above fully named content.

In case of forming this base pattern A, it is desirable to immerse thepipe 1 in a tank of a Trichlene or the like prior to connecting thispipe 1 with said bend pipe 3 as is clearly shown in FIG. l, so that boththe inner circumferential surface and the outer circumferential surfaceof the pipe 1 are thoroughly cleansed and removed of fat. Secondly, thebase pattern A formed in the above-mentioned manner is placed on aconveyor system 10 and transferred through a hot blast furnace 11whereby the pipe 1 and the water sealed therein are heated together fromthe outside of the base pattern A until the temperature of the waterexceeds the boiling point. The temperature at which the pipe 1 is heatedin the hot blast furnace 11 is subject to the diameter and thickness ofthe pipe 1, and in a general way, it is most suitable to be about230-270 C. The time when the base pattern A is conveyed through the hotblast furnace 11 is also subject to the diameter and thickness of thepipe 1, and in a general way, it is most suitable to be between and 40minutes. Incidentally, our experiments have obtained the best result forinstance when the base pattern A composed of the copper-make pipe of 0.4m./m. thick and in diameter was conveyed in half an hour through the hotblast furnace 11 heated up to 250 C. By using the hot blast furnace 11,the method of this invention provides such advantages that it ispossible not only to readily and controllably secure a high-temperaturenecessary for inflating the base pattern A but as well to heat the outersurface of this base pattern A at a uniform temperature, without havinga bad influence upon the fins 2. As the whole body of the base pattern Ais heated from the outside in said manner, each surface of the fins 2mounted in the base pattern A is heated over its maximum area; by thisendothermic agency of the fins 2, the thermal energy is effectively andequally conducted into the water sealed in the pipe 1 whereby the watercommences to be boiled simultaneously.

When the water has been overheated enough to exceed the boiling point,it begins to be gasified into a saturated vapor with the result ofincreasing in its cubic volume. And if said saturated vapor stillcontinues to be heated, it will be changed from the dry saturated vaporinto a superheated vapor; and if furthermore heated, this superheatedvapor will endlessly continue to increase in its cubic volume. Thus theaim of the present invention is at inflating the pipe by using thepeculiar nature of the superheated vapor that tends to boundlesslyswell.

According to the method of this invention, therefore, it is remarkableenough that the cubic expansion of the pipe of such a small diameter forexample, as a quarter inch is made quite possible in an easy and exactmanner which has so far been accepted as being technically beyond theconventional methods. This is possible because the base pattern A, ormore in particular, the fins 2, is heated from the outside so that thethermal energy is very effectively conducted from the fins direct to thepipe 1 through the heating surface area of the fins 2. Further thisinvention provides the advantages in that the pipe portion with whichthe fins are in contact can be very effectively inflated because it isthe endothermic agency of the fins that is used for inflating the pipe,and that the bend pipe or any similar curved portion with which the finsare out of contact is restrictively inflated to less extent than saidpipe portion which is in contact with the fins; consequently said bendpipe is prevented from such an unnecessary inflation as to be distortedor broken down.

After the pipe 1 has been inflated enough to rigidly connect the fins 2therewith, the pipe 1 and the fins 2 are gradually cooled by means of ablower or in a water cistern 62; and then the opening ends 1' and 1" ofthe sealingly closed pipe 1 are opened to drain the water sealed in thispipe 1. This drainage of the water is accomplished, for example, byforcing the highpressure air into the pipe from one of said opening ends1' and 1''. In the second place, the waterdrained pipe 1 undergoes adeliberate overhaul and then is dried by means of a desiccator whereby aheat exchanger is completely manufactured.

What is to be remarked in this respect is the employment of the fins 2having the constructions shown in FIG. 4 thru 7; this employment of saidfins 2 is especially imperative in the method the present inventionsince the latter aims at making the best of the endothermic agency ofthe pipe 1 which ahsorbs the thermal energy conducted from the fins 2.Namely, the fins 2 shown in FIG. 4 and 5 are provided with protrusions15 of almost triangular shape regularly spaced between the holes 2' ofthe fins 2 through which the pipes are inserted. Each of saidprotrusions 15 has a slot 16 or a crevice provided along the base ofsaid triangle opposed to the vertex thereof. The positional direction ofthese protrusions 15 is not especially limited; but it is desirable todispose these protrusions 15 in such a position that each vertex ofthese triangles orients in the direction where the heated air or thecooled air is passing.

Said slot 16 serves as an opening communicating with closely spacedneighboring fins 2. When the fins 2 formed in this manner are conveyedinto the hot blast furnace 11, they spread out the flow of the hot blastand disperse same through each vertex of the triangular protrusions 15of the fins 2; and a certain quantity of the dispersed hot blast passesthrough the slot 16 and is exchanged with the hot blast flowing over theneighboring fins 2 thereby to cause a turbulent current of air withinthese fins 2 with the result of enhancing the heatexchanging effect tosecure a very high-endothermic agency of the fins.

In addition, the heating surface per unit area is greatly increased dueto the formation of said protrusions 15 so that, coupled with saidendothermic agency of the fins 2, the water sealed in the pipe 1 isheated effectively in a very short time, and consequently the practicalutility of the present invention is enhanced more definitely. in placeof the above-mentioned fins 2, those fins having the constructions shownin FIGS. 6 and 7 are also able to secure the same effect that has beenmentioned above. Namely, the constructions of said fins 2 in FIGS. 6 and7 are different from that of the above-mentioned fins 2 in that aplurality of semispherical protrusions 17 are formed in a regular spacebetween a plurality of holes through which the pipes 1 are inserted, andthat slots 18 are formed so as to connect the mutually neighboringprotrusions 17. Said semispherical protrusions 17 are formed on the fins2 in order to provide thereon as the largest heating surface area aspossible and at the same time help the flow of the hot blast passswiftly from every direction. Further said slots 18 are formed in orderto provide on a single fin 2 with a plurality of independent heatingsurfaces; therefore, due to the slots 18 for interconnecting theprotrusions 17, the heating surface of each independent unit thusproduced therefore has, so to speak, a combination of many miniaturefins.

Accordingly, when the fin 2 form in this manner is adopted, the hotblast is spreaded out and dispersed through the protrusions 17 of thisfins 2, though not exchanged with the hot blast flowing over theneighboring fins 2, thereby securing the same high heat-exchangingeffect that has been referred to above. On the top of that, this fin 2can obtain the same result that is obtainable when several miniaturefins or several tens of miniature fins are used in combination, andsecure a by far higher heat exchanging efficiency than that of theconventional single unit-type fin, consequently inflating the pipe in avery short time with the same high efficiency as has been justmentioned.

The method of the present invention is practically made applicablebecause the base pattern A is fonned in the beginning and then heatedfrom the outside so as to cubically expand the pipe by use of theendothermic agency of the fin and also because said fin is formed in theabove-mentioned manner. The employment of such a fin makes it possibleto secure a highly efficient function especially when a heat exchangeris just in manufacture and when such a heat exchanger is practically inuse. In case the protrusions are formed on the fin, they work to enhancethe hardness of the fin surface. Further it is to be noted that byapplying the thermal inflation to the present invention, the device formanufacturing a heat exchanger can be not merely constructed in muchsimplified structure but as well operated in an easy manner.

This invention is not altogether restricted within the constructionsdisclosed herein, since what have been disclosed in this specificationare not to limit the purview of the invention but rather illustrative ofthe invention.

What is claimed is:

l. A method of manufacturing a finned-tube-type assembly heat exchangercomprising the steps of A. providing a plurality of fins, each of saidfins substantially consisting of a flat sheet of metal having therein aplurality of holes of particular diameters and a plurality of raisedportions located in the vicinity of said holes;

B. providing a plurality of lengths of pipe and assembling said fins andsaid lengths of pipe by means of fitting said lengths of pipe throughsaid fins, said lengths of pipe having diameters smaller than saiddiameters of corresponding holes;

C. interconnecting said pipes to form a single passageway;

D. closing tightly one end of said interconnected pipes;

E. filling said interconnected pipes with liquid;

F. closing tightly the other end of said interconnected pipes;

G. heating at least said fins thereby to transmit heat from said fins tosaid pipes until said liquid is heated above its boiling point andconverted to superheated vapor thereby to enlarge the diameter of saidpipes by cubic expansion of said vapor and tightly bind the outerperipheries of said pipes to the inner peripheries of said holes;

H. cooling the expanded assembly; and

l. removing said liquid from the assembly.

2. Method of claim 1, wherein said raised portions of said fins aregenerally shaped to have three sides with one side being separated fromsaid sheet, and the other two sides being joined together and adjacentto respective ones of said holes.

3. Method of claim 1, wherein said raised portions are semispherical inshape and located between selected pairs of said holes and wherein saidsheet contains slots between selected pairs of said semispherical shapedraised portions.

4. Method of claim 1, wherein said pipes are hairpin-type pipes or bentpi es. I

5. Method 0 claim 1, wherein said filling of said closed Interconnectedpipes with said liquid is done under pressure of about 25 KgJcm. therebyto remove air bubbles from said closed interconnected pipes.

6. Method of claim 1, wherein prior to said heating said pipes and saidfins are cleaned.

7. Method of claim 1, wherein said liquid is water and said heating isat a temperature within the range of between 230 and 270 C. for a periodof between 20 to 40 minutes.

8. Method of claim 1, wherein said pipes are of copper or copper alloy,and said fins are of aluminum or aluminum alloy.

9. Method of claim 1, wherein said heating is accomplished bycirculating hot air unto at least said raised portions of said fins.

1. A method of manufacturing a finned-tube-type assembly heat exchangercomprising the steps of A. providing a plurality of fins, each of saidfins substantially consisting of a flat sheet of metal having therein aplurality of holes of particular diameters and a plurality of raisedportions located in the vicinity of said holes; B. providing a pluralityof lengths of pipe and assembling said fins and said lengths of pipe bymeans of fitting said lengths of pipe through said fins, said lengths ofpipe having diameters smaller than said diameters of correspondingholes; C. interconnecting said pipes to form a single passageway; D.closing tightly one end of said interconnected pipes; E. filling saidinterconnected pipes with liquid; F. closing tightly the other end ofsaid interconnected pipes; G. heating at least said fins thereby totransmit heat from said fins to said pipes until said liquid is heatedabove its boiling point and converted to superheated vapor thereby toenlarge the diameter of said pipes by cubic expansion of said vapor andtightly bind the outer peripheries of said pipes to the innerperipheries of said holes; H. cooling the expanded assembly; and I.removing said liquid from the assembly.
 2. Method of claim 1, whereinsaid raised portions of said fins are generally shaped to have threesides with one side being separated from said sheet, and the other twosides being joined together and adjacent to respective ones of saidholes.
 3. Method of claim 1, wherein said raised portions aresemispherical in shape and located between selected pairs of said holesand wherein said sheet contains slots between selected pairs of saidsemispherical shaped raised portions.
 4. Method of claim 1, wherein saidpipes are hairpin-type pipes or bent pipes.
 5. Method of claim 1,wherein said filling of said closed interconnected pipes with saidliquid is done under pressure of about 25 Kg./cm.2 thereby to remove airbubbles from said closed interconnected pipes.
 6. Method of claim 1,wherein prior to said heating said pipes and said fins are cleaned. 7.Method of claim 1, wherein said liquid is water and said heating is at atemperature within the range of between 230* and 270* C. for a period ofbetween 20 to 40 minutes.
 8. Method of claim 1, wherein said pipes areof copper or copper alloy, and said fins are of aluminum or aluminumalloy.
 9. Method of claim 1, wherein said heating is accomplished bycirculating hot air unto at least said raised portions of said fins.